Method of compressing gas and apparatus therefor



s, 1924. 1,480,111 E. A. RlX

METHOD OF COMPRESSING GAS AND APPARATUS THEREFOR Find July 15. 1922 v INVENTOR. Edward A. R112:

A TTO Patented Jan. 8, 1924:.

UNITED STATES EDWARD A. RIX, OF SAN FRANCISCO, CALIFORNIA.

IVIETHOD OF COIVIPRESSING GAS AND APPARATUS THEREFOR. I

Application filed July 13,

To (LZZ whom it may concern:

Be it known that I, EDWARD A. Rix, a citizen of the United States, residing at the city and county of San Francisco and State of California, have invented new and useful Improvements in Methods of Compressing Gas and Apparatus Therefor, of which the following is a specification.

This invention relates to a method of compressing gas and an apparatus therefor.

in oil fields where gas is tapped that is wet or carries gasoline in vapor form, it is common practice to employ a reducing valve and to permit the gas to escape under a pressure of approximately 50 pounds gauge, this being true no matter how much in excess of this pressure a well may be capable of delivering the gas, the reason be ing that the petroleum production of the well is least interfered with when the gas escaping is maintained at this pressure or less. The gas escaping or discharging from the well under approximately 50 pounds pressure gauge is delivered to a gas compressor and is here boosted 300 pounds pressure gauge. It is then passed through cooling coils and absorbers to precipitate the gasoline vapor in the form of liquid gasoline and the gas thus relieved of the vapor is delivered to mains and is conveyed. through these mains in many instancesseveral hundred miles to the larger cities where the gas is employed for industrial and public utility purposes. Formerly large gas compressors were installed to compress the gas but it was found that when the wells were no longer productive that the expense of moving large plants of this character to other wells was burdensome and expensive, and as the result thereof a standard gas compressing unit has come to be generally adopted. These standard gas compressing units consist of duplex belt driven compressors driven by 160 H. P. gas engines. Practice has determined that these compressors should be equipped with two 8 inch diameter by 16 inch stroke single stage cylinders'when the gas pressure delivered thereto is J50 pounds pressure gauge. Such compressors operate at 150 R. P. M. and 300 pounds final pressure and they will approximate 1200 cubic feet of free gas and absorb all the power of 160 H. P. engines under such conditions.

its the pressure in the wells falls below 50 pounds pressure and on down to atmos- 1922. Serial no. 574,622.

pheric pressure, various combinations of larger diameter cylinders are placed on the compressors until when the gas pressure approximates 5 pounds intake pressure or less, the compressors become two-stage compressors with 16 inch diameter low pressure cylinder and 8 inch diameter high pressure cylinder, the stroke remaining constant or 16 inches. t is found that when this combination of cylinders is employed that 560 cubic feet of free gas at 300 pounds pressure are delivered and that all the power of the gas engines is consumed.

The difference in the quantity of free gas compressed between the extremes of 50 pounds pressure and zero or atmospheric pressure, to-wit, from 1200 to 560 cubic feet, represents the work done by the gas itself in entering the 8 inch diameter single stage cylinders at 50 pounds pressure. Experience has also determined that much time is lost and a large expense is incurred in changing and providing the cylinders of varying size, and also in providing repair parts for the cyliders of varying size. Experience has also determined that when the cycle of changes has been completed and the 16 x 8 x 16 two stage machine is finally developed that it has cost at least two prices and that much loss in time and output has been encountered.

My invention involves a method of compressing the gas and an apparatus therefor,

and it consists in installing the 16 x 8 x 16 two-stage cylinders immediately and equip ping the low pressure cylinder with a variable pressure device or out oif mechanism which will enable all intake pressures from 50 pounds gauge to zero or atmospheric pressure to be delivered to the compressor, causing the compressor to discharge from 1200 to 560 cubic feet of free gas per minute at 300 pounds pressure and with a slightly less expenditure of'power when comparison is made with the old method just referred to. More specifically stated this is accomplished by feeding the discharging gas from the well to the inlet valves of the compressor through a suitable form of cut off valve mechanism which may be best adapted. to the purpose, thus making the low pres sure cylinder an expansion engine on one side and a compressor on the other and alter-f nating these cycles at each revolution.

One form of compressor or apparatus suitable for the method involved is illus- "cylinder.

trated in the accompanying drawing, in which the figure is a horizontal, longitudinal section of a two-stage compressor showing the low stage cylinder equipped with the cut off valve mechanism whereby the volume of admitted during each suction stroke is regulated.

7 Referring to the drawing in detail, A and B indicate the low pressure and high pressure cylinders, respectively, 3 the inlet valves in the respective cylinders, 4-. the discharge valves, 5 the inlet air passage to the low pressure cylinder, 6 the inlet air passage to the high pressure cylinder, 7 the discharge passage in the low pressure cylinder, 8 the discharge passage in the high pressure cylinder, and 9 an inter cooler of suitable construction which connects the discharge passage of the low pressure cylinder with the inlet passage of the high pressure Each cylinder is provided with a piston as indicated and these are in turn driven from a main driving shaft C by means of cranks, connecting rods, cross heads and piston rods in the usual manner. The respective cylinders and the heads employed in connection with the same are water cooled in the usual manner and the shaft C is preferably driven by means of a pulley and belt from 160 H. P. gas engine not here illustrated.

Forming an integral part of the low pressure cylinder or suitably secured thereto is a valve chest 10 in which are slidably mounted the cut oil' valves, and slidable exterior thereof is the main valve 11. The cut off valves are indicated at 12, there being two employed, which are adapted to be moved to or away from each other by means of a right and left hand threaded rod 13. This rod is turned by means of a hand wheel. 14;, which is connected to the valve rod by a sliding feather and slot, and employed inconjunction therewith is an index mechanism i l, whereby the amount of cut oil may be visibly indicated. The entire valve mechanism shown is in reality nothing more or less than a standard form of cut off valve, known as the Meyers cut off valve. The main valve is a sleeve valve having ports formed therein adapted to align with seat ports .20 and this valve is reciprocated by an eccentric 15. which is con nected with an eccentric rod 1 6. The cut off valves are reciprocated by the cut off eccentric 17 and they are connected thereto by the cut off eccentric rod 18, the valve rod 13 being connected with the rod 18 by means of a ball and socket connection as shown to permit turning movement to be imparted to the rod 13 by means of the hand wheel 14. The cut off valves are circular in cross section'and are balanced, and re quire merely sufiicient power during operation to overcome their sliding friction. i1.

small leakage in a valve of this character makes comoaratively little difference because the valves are disposed in the inlet passage. When the cut off valves are drawn lose together the main valve ports are clear and no obstruction is offered the main valve which is in communication with the inlet poppet valves, but as the cut off valves are separated witn relation to each other they interfere or cut off the main valve openings at predetermined points indicated on the scale or index 1i, and the amount of gas admitted during each suction stroke is thus controlled.

It will is noted that the main valve has inlet ports only and thus differs from the ordinary slide valve in a steam engine, which employs both inlet and exhaust ports. It will further be noted that this variable out off mechanism operates entirely inde pendent of the compressor cylinder valves and as such has nothing to do with the normal functioning of the compressor cylinder, the function of the cut off valve mechanism being only that of controlling the amount of gas admitted, or in other words preventing an excess volume or pressure which might overload the motor.

By calculation first, and then by experience, a suitable chart may be made which will indicate the proper out off for each 5 pounds drop of pressure in the incon'iing gas, that is the entire range between 50 pounds and atmospheric pressure. The operator by referring to this chart, and noting the pressure of the incoming gas, may in this manner set the cut off mechanism by means of the hand. wheel until the proper adjustment is obtained and such regulation of the valve mechanism may take place without stopping the compressor.

1 give herewith a comparative set of calculations for both the old and the new systems, showing the power required in each cylinder and the work obtained from the gas, and l have chosen the maximum condi tions as to pressure and volume and in making these calculations the formulae for air has been employed instead of gas, inasmuch as the results are nearly the same and air is a perfect gas, and also due to the fact that the formulaepertaining to the compres sion and expansion of air are more familiar to all. The old system heretofore referred to hegius operation with two 8 inch diameter 16 inch stroke single stage cylinders having a piston speed of approximately 400 feet and employing an intake pressure of gas approximating 50 pounds gauge, and as a consequence thereof discharging said gas at 300 pounds pressure. The power required tocompress the gas is 220 H. P. and the work realized by the intake pressure of 50 pounds is 60 H. P. The diiference. or 160 H. P, that required to be furnished by the gas engine and the quantity of free gas discharged from the compressor is under these conditions 1200 cubic feet.

In my system the operation starts with a two-stage 16- X 8. 16 inch stroke compressor, the piston speed being 400 feet. The intake pressure of the gas on the low pressure cylinder is pounds, and under this condition cut off by means of the valve mechanism will take place at of the stroke. This, in order to insure the same delivery and volume of gas that the two 8 inch cylinders require in the old system. The gas after being cut off at one-half stroke expands isothermally on account of the heated cylinder to 17 pounds gauge. The work realized by the gas thus admitted is 92 H. P. The gas is then compressed to approximately 100 pounds gauge, which requires 154 H. P. of work during the compression stroke. The difference between these amounts, or 62 H. P., is the net work in the low pressure cylinder which the gas engine has to supply. The gas discharging from the low pressure cylinder at approxi- 'mately 100 pounds pressure enters the high pressure cylinder which is 8?; inches in diameter and here exerts a working energy approximating 68 H. P. The work of compressing this gas requires 159 H. P. and the net work is the difference between these two sums, or 91 H. P., which the gas engine supplies.

The low pressure cylinder requires 62 H. P. The high pressure cylinder requires 91 H. P.

Making a total of 153 H. P.

to deliver 1200 cubic feet of free gas at 300 pounds pressure. This amounts to a saving of 7 H. P., and also eliminates the changing of the cylinders when comparison is made with the old system of compression. It might be suggested throttling the intake from 50 pounds to zero would enable the two-stage to operate. This is true, but for a delivery of 560 cubic feet only, the work in the gas being entirely lost.

In compressing gas by my system, the 100 pounds intercooler pressure obtained will cause considerable gasoline to be precipitated or condensed and reduces the quantity of gas delivered by the high pressure cylinder by 4. cubic feet for each pound condensed and as this is not compressed to 300 pounds pressure that much working energy is saved. I therefore estimate that with the two power savings mentioned above, that the total net saving of power by my system will under the maximum condition of operation as cited, ap proximate 10 to 15 per cent. This saving will of course be gradually lessened as the intake pressure drops. The cut off valve will be backed completely away from the main valve ports, when the pressure reaches zero, when the low or atmospheric pressure is reached and will then be inoperative and the old and new systems will be identical as far as, efficiency and capacity are concerned. WVhen this happens the eccentric rods may be removed and the main sleeve valve may or may not be pulled out of the valve box. The variable pressure or out off inechanism may be constructed as an independent unit so as to be conveniently attached to any cylinder. There are no clearance losses involved and it is for this reason not necessary that the cut off valve mechanism be placed immediately on the cylinder or adjacent the same, and as the entire valve mechanism is counter-balanced, as far as the gases are concerned, it is obvious that only sufficient power to overcome the inertia and friction of the moving valves is all the power required.

Having thus described my invention, what I claim and desire to secure by Letters Patent is 1. In a compressor of the character described the combination with the inlet ports of the low pressure cylinder, of means for regulating the volume of gas under pressure admitted during a portion of each suction stroke.

2. In a compressing unit of the character described the combination with the inlet ports of the low pressure cylinder, of means connecting said inlet ports with a source of gas supply delivering gas under varying pressures, and means cooperating with said delivering means for controlling the volume of gas delivered to the low pressure cylinder during each suction stroke.

3. In a compressing unit of the character described the combination with the inlet ports of the low pressure cylinder, of means connecting said inlet ports with a source of gas supply delivering gas under varying pressures, and means cooperating with said delivering means controlling the volume of gas delivered to the low pressure cylinder during each suction stroke, said means being adjustable to deliver varying volumes of gas.

at. In a compressing unit ofthe character described a low pressure compressing cylinder and a cut off valve cooperating there with adapted to regulate the volume of gas admitted during each suction stroke.

5. In. a compressing unit of the character described a low pressure compressing cylinder and a cut off valve cooperating therewith adapted to regulate the volume of gas admitted during each suction stroke, said out off valve being adjustable to vary the volume of gas admitted during each suction stroke.

6. A method of compressing gas delivered to a compressor under pressure, which consist s in regulating the volume of gas ad mitted during each suction stroke of the compressor and then compressing the gas thus. admitted.

7. A method of compressing gas delivered to a compressor under pressure, which. consists in admitting the gas duringa portion of the suction stroke of the compressor, permittingthe gas thus admitted to exert its expanding force during the; remaining portion of the stroke, and then compressing the gas during the return stroke.

Leann 1'? 8. A method ofcompressing gas deiivere'i to a compressor under-pressure, Which consists in admitting the gas during a portion of the suction stroke of the compressor, per-- mitting the gas thus admitted to exert its expanding force during the remaining portion of the stroke, compressing the gas during the return stroke and then discharging 20 the gas during said stroke at a higher pressure than that under which it Was admitted during the suction stroke.

EDWARD A. RIXQ 

